chro·mo·som·al

chromosomal

chro·mo·som·al

chro·mo·som·al

chromosomal,

adj relating to chromosome, or a configuration within the cell's nucleus that contains a linear thread of DNA that conveys genetic data.

chromosomal

emanating from or pertaining to chromosome.

chromosomal aberration

see chromosomal abnormality (below).

chromosomal abnormality

abnormal karyotype; abnormalities can be detected before birth by means of amniocentesis, or after birth, but many are probably never observed because they cause death and disposal of the fetus. The abnormalities are either of number, or of composition of the individual chromosomes. Monosomy and trisomy are examples of numerical abnormalities. Translocations are examples of abnormalities of structure where parts of one chromosome have been transferred to another. The cause of these abnormalities is not known. Their importance is that many of them are linked with structural or functional defects of the animal body. The best known ones in veterinary medicine are those that are related to infertility, e.g. translocation 1/29, translocation 27/29.

chromosomal analysis

fetal cells obtained by amniocentesis or lymphocytes from a blood sample can be cultured in the laboratory until they divide. Cell division is arrested in mid-metaphase by the drug Colcemid, a derivative of colchicine. The chromosomes can be stained by one of several techniques that produce a distinct pattern of light and dark bands along the chromosomes, and each chromosome can be recognized by its size and banding pattern. The chromosomal characteristics of an animal are referred to as its karyotype. This also refers to a photomicrograph of a cell nucleus that is cut apart and rearranged so that the individual chromosomes are in order and labeled. The autosomes are numbered roughly in order of decreasing length. The sex chromosomes are labeled X and Y. Karyotyping is useful in determining the presence of chromosome defects.

The new technique will be added to the company's EmbryVu testing service, making it the first NGS-based PGS platform that can identify key chromosomal abnormalities including haploidy, triploidy, and some forms of tetraploidy and UPiD.

Doctors say that genetics plays an important role in maintenance of normal spermatogenesis ( sperm production) and in about 30 per cent of infertile males, chromosomal abnormalities and gene mutations have been associated with infertility.

The nuchal translucency (NT), which is the fluid behind the foetal neck, is measured between 11-14 weeks to determine the risk of the foetus having not only a chromosomal abnormality, but also cardiac, other structural abnormality in the foetus, or a genetic disorder.

Assessment of foetal nuchal translucency and first trimester serum biochemistry has proven to be a far superior screening test, detecting 90 per cent of foetuses with chromosomal abnormalities at a false positive rate of three to five per cent, Dr Ramanathan said.

In conjunction, a December 2012 joint committee opinion from the American Congress of Obstetricians and Gynecologists and the Society of Maternal Fetal Medicine supports the use of cell-free fetal DNA testing as an option for primary screening for pregnant women at increased risk of aneuploidy (abnormal chromosomal number), including those 35 years of age or older or who have a history of ultrasound abnormalities in pregnancy.

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